1. Field of the Invention
This invention relates to a weldless method of joining pipe segments to form a pipeline of indeterminate length. More particularly, the invention relates to a friction fit pipe joint which leaves an interior bore of uniform diameter within the pipeline.
2. Description of the Prior Art
There exist a variety of methods of joining pipe segments to form a pipeline of indeterminate length. Common techniques for joining such pipe segments include various welding techniques, threaded joining techniques and interference fit techniques.
Welding techniques for forming pipelines to be used in subsea applications can be time-consuming and expensive. Additionally, the pipeline must be examined, usually by x-ray techniques, to confirm that it is satisfactory and suitable for use in subsea applications. Similarly, threaded pipe joining techniques have not found acceptance in sub-sea operations because they too are costly for the application.
A pipeline joining technique of recent popularity is that which utilizes friction or interference fitting. Common among such joining methods are the so-called "bell and pin" techniques and sleeve joining techniques.
In the "bell and pin" techniques the pipe ends are machined such that one end of a pipe is of an enlarged diameter, and formed into a bell shape, while the other end is tapered to a pin shape. Pipe segments are joined by interferingly fitting a pin end into a bell end. Although less expensive and less time-consuming than welding or threading methods, a disadvantage of these techniques is that the joint may be incapable of withstanding high pressure and may either leak or separate when the conduit is subjected to higher interior pressures. Such techniques are disclosed in U.S Pat. Nos. 4,064,619; 4,257,155; and 4,277,091.
In sleeve joining techniques the ends of pipe segments are interferingly joined within an external sleeve. Such techniques often involve tapering or contouring of either the interior bore of the sleeve or the pipe ends. Usually, the pipe joints formed by these techniques have protrusions which extend into the interior bore of the pipeline. U.S. Pat. Nos. 3,343,252; 3,476,413; 4,295,526; and 4,389,763 disclose such techniques.
Despite the above disclosures there remains a need for an effective technique of rapidly and economically fitting pipe segments, of sufficient strength for sub-sea applications, to form a pipeline having an interior pipeline bore which is smooth and free of protrusions and obstructions.